1. Field of the Invention
The present invention relates to visible light-sensitive compositions, as well as to formation processes, using the compositions, for patterns useful to circuit formation of electronic devices, materials for printing etc.
2. Description of the Prior Art
Currently, positive type photoresists are widely used for formation of circuit patterns of electronic devices etc. As positive type resist compositions used for these applications, in many cases, combinations of an alkali-soluble novolac resins and a quinone diazide compound as a photosensitizer, are used.
These compositions utilize a reaction in which the quinone diazide group is photo-decomposed when irradiated with an ultraviolet light and forms an indenecarboxylic acid via a ketone.
The resists using this quinone diazide compound, however, are weakly photoreactive to a visible light and, hence, there are problems of insufficient resolution, etc., in the case a formation of a very fine pattern is necessary.
The present inventors previously proposed, as positive type photosensitive compositions replacing these other prior compositions, a composition sensitive also to a visible light comprising a polymer having carboxyl group(s), a compound having a plurarity of vinyl ether groups, and a compound which is decomposed and generates an acid when irradiated with an actinic ray (Japanese Laid-open Publication No. 295064/1994) and a visible light-sensitive composition comprising a polymer having carboxyl group(s) and hydroxyphenyl group(s), a compound having a plurarity of vinyl ether groups, and a compound which is decomposed and generates an acid when irradiated with an actinic ray (Japanese Laid-open Publication No. 146552/1995=U.S. Pat. No. 5,496,678).
These compositions are photosensitive compositions which function according to a mechanism wherein the film formed from them becomes insoluble in solvents and aqueous alkaline solutions through crosslinking by an addition reaction between carboxyl group(s) and vinyl either group(s) when heated. When the composition is further irradiated with an actinic ray and then heated, the exposed portions become soluble in solvents and aqueous alkaline solutions again as the crosslinked structure is severed by the catalytic action of the acid generated by the irradiation.
These compositions have advantages such as having high transparency to actinic rays, because they need not contain a large amount of a functional group of high extinction coefficient unlike resists using quinone diazide as a photosensitizer and having high sensitivity as positive type photosensitive composition because the acid generated at the exposed portions acts as catalyst, when heated, to sever the crosslinked structure in the form of a chain reaction.
However, the heating time is required to be shortened in respect of productivity, when these photosensitive compositions are coated on a substrate and heated for crosslinking. When a shortening of the time is tried by heating at a higher temperature than 100.degree. C., there is the problem that the compound, which generates an acid when irradiated with an actinic ray, existing in said photosensitive composition, generates an acid before being irradiated by a visible light and, thus, the whole formed film is dissolved when developed. Therefore, an improvement of the thermal stability of said photosensitive composition is strongly demanded in this technical field.
The present inventors made an intensive study to solve problems the above-mentioned photosensitive compositions have. As a result, they have found that the above-mentioned problems can be solved by using naphthalimidylsulphonate, as the compound which is decomposed and generates an acid when irradiated with a visible light, in combination with a sensitizing dye and completed the present invention.